Chestband Analysis of Human Tolerance to Side Impact

A series of 26 human cadaver tests with chestband instrumentation and accelerometers were completed to assess side impact injury tolerance. A Heidelberg-type sled test system was used with thorax, abdomen, and pelvic load plates. Tests were conducted at the Medical College of Wisconsin and through the Ohio State University College of Medicine at the NHTSA Vehicle Research and Test Center at two different velocities: 24 kph and 32 kph. Test conditions included rigid wall, padded wall, and pelvic offset. Accelerations were recorded at rib 4, rib 8, and T12. Up to three chestbands were placed on each surrogate. Chest deflections were derived by computing chest contours at every millisecond throughout the event. The derived chest deflection-time curves were differentiated to obtain velocity of chest compression. Injury criteria including ASA15N, TTI, normalized chest deflection, and VC were computed. Resulting injuries ranged from AIS = 0 to AIS = 5. Rib fractures were the most common injury. In general, measured parameters were higher for high velocity tests compared to low velocity tests. The padded wall condition produced lower peak forces, accelerations, and chest deflections compared to the rigid wall condition. Using logistic regression analysis, the ASA15N parameter yielded a 50% probability of AIS ≥ 4 injury at 35.5 with a p-value of 0.0662; the TTI parameter yielded a 50% probability of AIS ≥ 4 injury at 169 with a p-value of 0.0004; the Max%C parameter yielded a 50% probability of AIS ≥ 4 injury at 30% with a p-value of 0.0146; the MaxVC parameter yielded a 50% probability of AIS ≥ 4 injury at 1.26 m/s with a p-value of 0.0107. A new injury criterion combining TTI and Max%C was derived. This criterion yielded the best statistical outcomes compared to any of the other injury criteria. The TTI*C criterion produced a 50% probability of AIS ≥ 4 injury at a value of 58 with a p-value of 0.0001. The present test protocol that includes extensive measurements of cadaver specimens provides a means to develop a most efficacious injury criterion for side impact.